The thermal response to high frequency (HF) electromagnetic energy, including radio frequency (RF) and even microwave (MW) energy, of olefin copolymers which contain carbon monoxide (CO) as a copolymer constituent is disclosed, e.g., in recent U.S. Pat. Nos. 4,600,614 4,601,948 4,640,865 4,660,354 4,671,992 4,678,713 4,762,731 4,766,035 4,787,194 4,728,566.
Patents showing the halogenation of ethylene polymers containing copolymerized carbon monoxide (CO) are U.S. Pat. Nos. 4,616,072 and 4,687,805.
The interest of the polymer and packaging industries in the beneficial thermal response (i.e., the RF-heatability, esp. MW-heatability) of the ethylene polymers containing copolymerized CO is on the increase and improvements which enhance or aid in regulating the thermal response (heating) are desired.
The prior art has used "lossy" materials, such as carbon or ferrites, as additives to polymers to induce or increase the loss factor of the polymers so as to induce or increase thermal response of the polymer to electromagnetic radiation energy, thereby causing a heat build-up in the polymer. These "lossy" materials have high loss factors and were often selected because of that property. Also there are reasons why one would wish to avoid the use of additives such as carbon or ferrites, such as for aesthetic or clarity purposes. In contradistinction to the use of additives having high loss factors to induce or increase the thermal response of a polymer to the effects of electromagnetic radiation energy, the present invention uses additives (also called "agents") which have very low loss factors and in so doing achieve a synergistic effect with the RF effect recently found to exist in CO-containing copolymers, as shown in the above-identified patents.